The owners of Maximum Security have filed a federal lawsuit seeking to have the horse reinstated as winner of the Kentucky Derby, several US media reports said on Wednesday.
Maximum Security was dramatically stripped of victory in the US horse racing showpiece at Churchill Downs on May 4 after stewards ruled he interfered with rival thoroughbreds after veering from the rail on the turn for home.
It was the first time in the 144-year history of the Kentucky Derby that the horse crossing the finish line first was denied victory for hindering a rival.
Country House, a 65-1 longshot that crossed the line 1 3/4 lengths behind Maximum Security was later declared the winner.
Maximum Security's owner Gary West however has strongly condemned the decision, accusing stewards of acting "non-transparently" in their decision to strip his horse of the win.
An appeal against the disqualification was dismissed by the Kentucky Horse Racing Commission last week after the body said there were no grounds for appeal.
That left a court action as the only realistic chance of the result being overturned.
In West's federal lawsuit, filed in the US District Court in Frankfort, Kentucky, late Tuesday, the disqualification was condemned as "bizarre and unconstitutional."
The lawsuit seeks to have the original order of the finish reversed "confirming that Maximum Security is the official winner of the Derby who remains undefeated."
The defendants in the case are listed as chief steward Barbara Borden and every member of the Horse Race Commission.
The Wests said the decision to disqualify Maximum Security breached a state law that says a court may overturn any state agency decision if it is "without support of substantial evidence" or is "arbitrary, capricious or characterized by abuse of discretion."
The case argues that Maximum Security had committed no racing offence, insisting the horse was "entitled as the leading horse to a path on the track of his choosing."
The filing asserts the decision cost bettors on Maximum Security more than $100 million.